It works well for our business situation, which is a 100% online company with employees scattered across various states. We can transfer calls to another employee even though the other employee may be on the other side of the country. The flow of the calls coming in can be changed as needed. Support has generally been helpful.
Their setup screen/dashboard is confusing. Over time, I've gotten accustomed to it and can find things better. (Fortunately, they don't change things about every time you log in, like GoDaddy, where it requires a constant search of, "So where did they move that function?")
We are a 100% online company with employees working out of their homes in various states. We needed a phone system that was unified, and RingCentral has solved that need. We have used RingCentral since we began the company six years ago.
I have a desk phone that RingCentral supplied (I probably bought it, but at any rate, it came from them and has their brand name on it). This is a VoIP phone, and I have a slow internet speed (3.5 Mbps download), so if I'm opening a web page while on the phone, the phone connection stutters pretty badly. But if I'm only using the phone, it's fine (usually). The desk phone works very well for me, enabling me to keep work calls separate from personal calls. Well, I think you can do that by using the RingCentral app on your cell phone, but at any rate, I prefer having the desk phone when I'm working.
Each employee on the team has their own extension and their own set of rules, related to how phone calls should flow during their office hours and when they're out of the office. We use a receptionist service, so the calls first go to the employee, and if no response within the specified time, it then goes to the receptionist service (according to the flow we have set up in RingCentral). But there are seemingly endless ways you can have the calls routed. It can be confusing to figure out how to set up, but RingCentral support has always cheerfully helped me set up the pattern I'm looking for if things are not working the way I expect.
We use RingCentral for our fax number. Phone calls and faxes are logged in the portal so that we have a record for everything.
Those are the main things I've used RingCentral for. I haven't used the iPhone app much, basically because I do most phone calls from my desk phone, so I have no opinion to give of the iPhone app. At one point -- I think before I got the desk phone -- I tried to use the "soft phone" in the web portal, but the sound broke up so terribly that it was unusable. That was several years ago, so that may have been fixed since then; once I got my desk phone, I had no need for that anymore.
We have been looking into integrating RingCentral with Zoho (our CRM). It looks like it would be beneficial.
We have an account representative who calls quarterly to check on our needs and help where needed.